Conventional “framed” side doors on passenger vehicles generally include a structural member extending around the top of the side window, typically referred to as a door frame. Among other things, the door frame provides support for glass run seals which in turn provide support and sealing function to the door glass when the glass is in the up position. Some vehicles have “frameless” door systems that do not have any structural member above the belt line to support the glass. These are typically used on vehicles with a folding or removable (convertible) top so that when the top is stowed and side windows are down there is unobstructed view out of the vehicle. Frameless doors are also used on some coupes and sedans to achieve certain styling objectives. On vehicles with frameless door systems, the upper edge of the door glass mates to a weather strip that is mounted to the vehicle body to provide sealing function. In order to maintain proper ability to open and close the door, the glass must be able to swing in and out of this weather strip freely. This architectural condition presents challenges to achieving desired water and air leakage (wind noise) performance, particularly at high vehicle speeds (80+ MPH). At these high speeds, aerodynamic loads on the glass tend to pull the glass away from the body, potentially reducing the ability to seal the vehicle (also known as glass “blow-out”).
Previous generations of frameless door systems relied on significant inboard preload of the glass into the body mounted weather strip to provide adequate sealing pressure and resistance to aerodynamic glass “blow out”. High levels of preload can cause premature seal wear during glass cycling, as well as other undesirable issues. A more modern solution has been to use an “indexing” window regulator system. Generally, these systems drop the side glass a short distance when the door is opened, then fully close it again when the door is closed. This changes the direction of glass engagement with the weather strip and allows overlap between the glass and a seal structural member (a.k.a. seal retainer) to help resist aerodynamic loads on the glass while maintaining door open ability. These indexing systems can generally provide a robust balance of glass “blow-out” performance and door open-ability. They also generally allow for relatively unhindered door opening even if the indexing system is not functioning, a characteristic that is especially important for egress of passengers after an accident. Even with the availability of modern indexing systems, achieving a balance between acceptable aerodynamic glass blow-out performance and door open-ability may be more challenging in some situations.
The following examples describe situations in which door opening abilities can be a challenge. 1.) In some vehicles with extremely high top speeds, the resulting higher aerodynamic loading on the glass may require increased engagement with the seal structural member, which in turn may result in issues with door open-ability (glass catching or dragging on seal structural member etc.). 2.) The automotive industry is moving toward thinner glass panels (for weight savings) and laminated glass constructions (for acoustic performance) which result in lower glass panel stiffness. Glass panel stiffness is a significant contributor to high speed aerodynamic blow out performance in a frameless glass system (stiffer is better). This situation may also require a higher level of seal structural member engagement to achieve acceptable aerodynamic blow out performance, which may result in issues with door open-ability (as above). 3.) Some vehicles have doors with non-traditional hinge angles or more complex opening motion where the doors swing upward in addition to (or instead of) outward upon opening. These types of doors can generally be found on high performance vehicles and are sometimes referred to as “scissor”, “butterfly” or “swan” doors. Systems such as these may require a more sophisticated index trigger mechanism or closer coordination between the window regulator and door latch to ensure that the glass has dropped sufficiently in time to allow the door to open freely under normal operating conditions. If situations arise where the glass indexing system fails (i.e. vehicle is involved in an accident, door glass is frozen, vehicle battery has low voltage or there is a failure within the electrical or mechanical system) it may be necessary to break the door glass to open the door, which is not an ideal situation. 4.) Vehicles with side door glass that is more vertical in orientation (front view angle—commonly referred to as “tumblehome” angle) generally have a smaller difference between glass blow out direction and door opening direction. This tends to shrink the design space available, likely resulting in a less robust balance between glass sealing, door open-ability and resistance to high-speed glass blow-out. 5.) Vehicles where the manufacturer desires to have a very small or no visible seal structural member (i.e. “flush glass” look) for appearance reasons.
Thus, a need exists for frameless door systems that meet the competing requirements of door opening ability and glass retention to reduce high speed wind noise.